In wireless communication applications the need for throughput and capacity keeps increasing over time. Wireless Internet Service Providers (WISPs) who installed their communication networks years ago have a large number of users with hardware running communication technologies that are difficult to upgrade without replacing the hardware. With a business need to increase throughput and capacity in these networks, the migration path to more efficient communication technologies is of great importance. In many cases the option of replacing all the radios in the entire communication network with new hardware is not feasible, because of the cost and the time needed to reach all the subscribers, during which service cannot be provided. In this scenario it is therefore necessary to support both the old and new communication technologies at the same time.
For example, in a wide area network, such as the Motorola Canopy™ communication system, with all radios supporting frequency shift keying (FSK) technology, the need for higher throughput and capacity may require the WISP to switch to the newly developed orthogonal frequency division multiplexing (OFDM) technology. However, it would be necessary to keep supporting the existing FSK subscriber modules, which may or may not be replaced by OFDM units over time. When new units are added to the network, they should support OFDM technology. In addition, any Access Point (AP) supporting FSK technology would need to be replaced by a dual mode FSK-OFDM AP which supports both groups of users.
One solution to this problem is to have two APs that time-multiplex slots from the old and new technologies. However, this solution does not adequately resolve the problem because it requires parameters from one technology to be selected according to the other technology. For example, the slot times need to be integer multiples of each other. In the FSK-OFDM case, this would lead to wasting air time. Also, the ratio between the times spent on either technology cannot be changed frame by frame. Although this solution describes a way for the two access points to communicate to each other and negotiate the number of slots assigned to each one, this negotiation takes several frame times. Although this solution could be acceptable for the technologies which are related to voice communications, in the case of data communications, the demand from one group of users can significantly change from one frame to the next.
Accordingly, there is a need to allow WISPs to upgrade their communication network without having to replace all the communication units at the same time. In particular, it would be of benefit to find a technique to support communication devices with different communication technologies within the same communication channel.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.